The invention relates to a process and an arrangement for producing a supporting body for a catalytic reactor for purifying exhaust gas, particularly of internal-combustion engines in motor vehicles. More specifically, the invention relates to such process and arrangement in which corrugated or corrugated and smooth metal strips are wound or folded to form adjacent layers and are provided with slots extending transversely to their longitudinal direction.
A process of this type is known from German unexamined published Application (DE-OS) No. 33 11 654 in which a catalyst supporting body is wound up spirally from smooth and/or corrugated sheet metal strips, which body is then fastened in a casing tube. The thus created ring-type composite of the supporting body is then provided with slots in the area of the wound metal strips by means of known cutting and removing methods, such as laser bean cutting or spark erosion. These slots extend through the wound part of the supporting body in the longitudinal direction and are arranged approximately radially or in the direction of filaments. By means of this measure, the interior ring-type composite can be divided into several sectors or segments which are free of a tension or stress-generating thermal expansion. It is known that supporting bodies for catalytic reactors, during operation, can be heated by means of the catalytic conversion of the exhaust gas, from an operating temperature of approximately 500.degree. C. locally over more or less large areas to temperatures of over 900.degree. C. However, the thick-walled casing tube surrounding them retains its relatively low operating temperature of approximately 300.degree. C. for a longer period of time. The thermal stress which may therefore be expected and which may result in a detaching of the wound body from the casing tube, can be avoided by the arrangement of such slots.
The disadvantage of this above-noted arrangement resides in the relatively high expenditures for arranging such slots.
An object of the invention is to develop a process and arrangement of the above-noted type such that the wound or folded composite of metal strips is provided with the possibility of a thermal expansion without the requirement of processing the supporting body again after its production.
In order to achieve this object, it is provided according to preferred embodiments of the invention that the slots are first worked directly into the metal strips in the form of incisions, and that the metal strips are only subsequently wound or folded to their final shape. As a result of this measure, every individual layer of the wound metal strip or strips receives a certain freedom of expansion. Although the finished supporting body, which is produced according to such a process, has no through-slots which extend approximately radially or in the shape of filaments, it has a plurality of slots, which as a rule are distributed on the cross-section relatively non-uniformly and which provide to each individual layer the possibility to expand and thus also prevent that the finished supporting body can be damaged in its construction by thermal stress. The producing of the new supporting body is relatively simple because it is sufficient, in the case of a corresponding production arrangement, such as has been used for winding, or for the folding of metal strips, to place a pair of cutting rollers directly in front of the actual winding or folding arrangement. By means of this pair of cutting rollers, the metal strip to be processed or the metal strips to be wound or folded are then incised in the desired manner.
The incisions themselves may be made in different ways according to various advantageous preferred embodiments of the invention as illustrated in the drawings. It is not only contemplated in certain preferred embodiments to place the incisions in each case from the direction of the longitudinal edges of the strips toward the inside, but it is also contemplated to incise the strips only in their center area. In all cases, possibilities to expand are provided for the strips which prevent damage to the supporting body caused by thermal expansion.